This application is based on and claims the priority under 35 U.S.C. xc2xa7119 of German Patent Application 199 44 124.3, filed on Sep. 15, 1999.
The invention relates to a ventilation valve with a breathing channel for a tank container and particularly a fuel tank of a helicopter. The ventilation valve contains a device to seal the breathing channel from the tank when a connecting means between the fuselage cell (especially the floor) and the tank container is loosened (as a result of a crash), whereby the device is arranged in a valve housing of the ventilation valve and has a movable seal element.
Many state of the art helicopters have a tank system that comprises, among other things, two tank containers. Both tank containers, which are also termed the main tank and the extraction tank or fuel feed tank, are arranged within a subfloor structure, whereby the subfloor structure is attached between the floor and the bottom shell of the fuselage. The main tank and extraction tank are arranged in the same plane and in a row one behind the other in the subfloor structure, with reference to the lengthwise axis of the helicopter. The main tank and extraction tank are connected via a connecting channel by a pump. Both tanks are also connected to each other via an overflow channel. The main tank has a much larger capacity. The extraction tank lies behind the main tank toward the rear of the helicopter. A fuel supply line leads from the extraction tank to the main engine of the helicopter, for supplying fuel from the extraction tank to the engine.
The main tank and extraction tank have a self-sealing ventilation valve that is connected to a breathing channel for the inflow and outflow of air. This breathing channel is directly above the top edge of the tank containers. The breathing channel can therefore fill up with fuel when the tank is full and there is a slight tilt to the tank containers. Such a known ventilation valve is described in German Patent 198 44 264 C1. The ventilation valve has a device to seal the breathing channel from the tank container when a crash impact causes the release or disruption of a connecting means between the fuselage cell (floor) and the tank container. The disadvantage of the state of the art arrangement is that the tank container of the helicopter with the prior art ventilation valve cannot be completely filled with fuel, so that the actual capacity of the tank containers cannot be fully utilized even though it is available as empty tank volume.
Due to the angle of the landing frame of a resting helicopter in relation to the surface on which it rests, the main tank and extraction tank are also angled or tilted relative to a horizontal plane when the helicopter rests on a horizontal surface. Particularly, the main tank is somewhat higher than the extraction tank.
When the helicopter is filled up with fuel while it is standing, fuel runs into the breathing channel (sometimes termed xe2x80x9cthe channelxe2x80x9d herein for short reference) due to the angle of the helicopter, and can block the breathing channel. In a typical conventional tank arrangement, the middle of a ventilation line is only a few millimeters (approximately 12 mm) above the top edge of the tank container or approximately 28 mm above the level of the ventilation holes. With this arrangement, the ventilation channels are filled with fuel when a full tank container is at a slight angle.
When the tank container is completely full, this problem also arises in forward horizontal flight when the extraction tank is somewhat higher than the main tank due to the flight position.
There is another familiar problem. When a filled-up helicopter stands for a while in the heat or is subjected to rapid temperature changes during flight, liquid fuel settles in the breathing channel due to the condensation of fuel vapor.
When there is too much fuel in the channel, the proper ventilation functioning of the breathing channel can be disturbed or interrupted.
In view of the above it is an object of the invention to allow the tank container of a helicopter to be filled essentially full, and to ensure the ongoing reliable functioning of the breathing channel. The invention further aims to avoid or overcome the other disadvantages of the prior art, and to achieve additional advantages, as are apparent from the present specification.
The above objects have been achieved according to the invention in a tank arrangement for a helicopter, including a first tank, a second tank, a first breathing channel connected to the first tank, a second breathing channel connected to the second tank, a connecting channel that connects and intercommunicates the first and second breathing channels with each other, and a first ventilation valve interposed between the first tank and the first breathing channel. The first ventilation valve includes a valve housing, and a device arranged in the housing to seal the valve or particularly the flow passage to the first breathing channel when a mechanical connection of the first tank is released from the first tank. The first ventilation valve further includes a movable seal comprising a valve ball that is so adapted and arranged to selectively seal the first breathing channel dependent on and responsive to the level of fuel in the first tank.
Particularly, the valve ball is a buoyant valve ball that buoyantly floats upward in or on the fuel as the level thereof rises into the first ventilation valve. This causes the valve ball to seal an opening or port from the first ventilation valve into the first breathing channel when the first tank is substantially full with fuel. Preferably, the valve ball can move freely through a stroke path in the hollow cylinder area within the valve housing extending from the safety device to the port opening of the valve into the breathing channel. In order to seal the port opening, the diameter of the valve ball is larger than that of the port opening.
The second tank may further be equipped with a second ventilation valve. This second ventilation valve of the second tank may have the same construction and arrangement as the first valve, or may be a simpler valve that includes the above mentioned safety device, but does not include the above-mentioned valve ball as the seal element. Thus, the second valve provided on the second tank and communicating into the second breathing channel will mechanically close the flow passage in the event of a disconnection of the tank from its mounting structure (e.g. due to a crash), but will not close or seal the valve as a result of the full fuel level of the second tank.
With the inventive arrangement, the tank containers can be filled completely without endangering the breathing of the tank system. The ventilation valve according to the invention is arranged in the extraction tank (i.e. the above mentioned first tank is preferably the extraction tank), while the second tank i.e. the main tank may still be equipped with the prior art ventilation valve. The invention also ensures that condensed fuel will not endanger the breathing or ventilation of the tank system. Even in flight and especially horizontal flight, at least one of the two ventilation channels will be available for the tank system to breath.